1. Field of the Invention
This invention relates to a photo-electric converting device and more particularly to a photo-electric converting device having a structure which provides high photo-electric converting efficiency.
The photo-electric converting device in accordance with this invention includes photo-electric converting devices having a pn junction therein such as a solar cell, a photo-detecting device and the other photo diode.
2. Description of the Related Art
In order to increase the converting efficiency of a photo-electric converting device having a pn junction, it is efficient to relatively decrease a pn junction area in comparison with a device area. To this end, in the prior art, one of the semiconductors which constitute a pn junction was formed in the shape of plural dots so that its area is smaller than that of the other semiconductor, thereby relatively decreasing the pn junction area in comparison with the device area. The photo-electric converting device having such a structure has been proposed in an article in IEEE, Photovoltaic Specialists Conference (1985) pp. 424-429.
Meanwhile, it is critical for improving the photo-electric converting efficiency of the photo-electric converting device having a pn junction that minority carriers generated due to light absorption efficiently reach the pn junction.
However, in the prior art mentioned above, as shown in FIG. 1, since emitters 12 are formed on a base layer 11 in the shape of plural dots to decrease the pn junction area, the minority carriers optically generated in a base layer can not effectively reach the pn junction unless the interval between the emitters are sufficiently smaller than the diffusion length of the minority carriers. However, if the emitter interval is decreased, the electrodes 13 which are provided on an emitter layer to collect the current from the emitters 12 must also be decreased in their interval and width. Thus, the prior art has a problem to be solved that it is difficult to form the electrodes with a high accuracy.